The present invention relates generally to an agricultural grinder-mixer and more specifically to an improved dust collection system for removing the finely ground crop material suspended in the air from the hammermill area, separating this material within the dust collector thereby allowing the material to settle out, directing the settled out material back into the top of the hammermill and then transferring it into the hammermill discharge auger for delivery into the mixing tank.
Grinder-mixers of the type commonly utilized today employ various dust collection systems to draw off the finely ground crop material particles that are suspended in the air from the area of the hammermill and cycle them through what is normally a centrifugal cyclone separator to centrifugally separate out the dust particles from the air. This technique permits the recovery of additional crop material which is then recycled down into the hammermill discharge auger or some type of transport means for delivery into the mixing tank. Numerous dust collection systems have been designed for this purpose with varying degrees of success. Regardless of the different designs that exist for agricultural grinder-mixer dust collection systems, all employ some sort of a suctioning device, such as a fan, to draw off the finely ground crop particles suspended in the air from an area generally adjacent the hammermill. The suctioning device or fan creates sufficient air flow to transport the suspended material to a particular collection and separating means.
The location of the fan in the dust collection system has even been the basis for variations in design approaches. Some designs have positioned a fan on the front side of the hammermill attached to the hammermill housing to minimize the amount of ground particles that are drawn off from the grain flow as it is transported rearwardly from the hammermill by the discharge auger into the mixing tank. This particular design arrangement ensures that primarily only the finely ground crop material particles of particular matter suspended in the air surrounding the hammermill are drawn off since the heavier less finely ground particles are conveyed rearwardly out of the back of the hammermill housing towards the mixing tank by the discharge auger. This placement of the fan is an improvement over those grinder-mixers which draw off the particulate crop material from the rear side of the hammermill. These latter grinder-mixers are much more likely to include in the air stream greater amounts of the less finely ground particles, even including portions of corn cobs, which are in the grain material flow being transported out the rear of the housing towards the mixing tank.
Other grinder-mixer designs employ dust collection systems which return the settled out particulate crop material from the cyclone separator back into the hammermill discharge or unloading auger intermediately of the hammermill and the mixing tank. This type of design, especially in grinder-mixers employing an air draw system from the rear of the hammermill, suffers from the disadvantage of tending to plug or clog the hammermill discharge auger at the point where the return chute feeds into the auger since a relatively large volume of crop material can be deposited into the discharge auger at that point. When the settled out crop material is added to the ground crop material flow already being transferred by the unloading auger, the auger quite frequently will become overloaded and plugging will occur, especially when the particulate matter being returned is interspersed with large clumps of crop material, such as corn cobs. An additional disadvantage of this type of a design for a dust collection system readily becomes apparent whenever an abundance of ground crop material accumulates in the bottom of the hammermill adjacent the discharge outlet above the discharge auger. Such a buildup of material plugs the hammermill and lowers its efficiency by decreasing the amount of crop material and air that can flow out of the discharge outlet. When this plugging occurs, a dust collection system of this design is in effect short circuited since the fan draws air directly from the discharge chute or duct of the separator, through the unloading auger, past the fan and into the separator. Since little or no air can pass through the hammermill due to the plugging, the air flow continues in a continuous loop never drawing air from the hammermill area with its suspended particulate matter.
Another design found on grinder-mixers utilizes a dust collection system that draws off the finely ground grain material that is suspended in the air from a chamber that is positioned atop an opening in the hammermill discharge auger. This design suffers the same basic disadvantage of tending to draw off the larger and generally heavier crop material, such as kernels of grain and portions of corn cobs, that already has been through the hammermill and is being transferred in the hammermill unloading auger to the mixing tank.
Still another variation in design draws the air from the hammermill housing, cycles it up into the dust collector and then returns the settled crop material back into the hammermill on the rear side of the housing adjacent the fan. This type of a system will not only maximize the amount of ground crop material that is drawn off by the suction of the fan into the air stream directed to the cyclone separator, but also causes the settled out crop material to cause excessive and uneven wear on the hammers of the hammermill by concentrating the returned material's entry on one edge of the hammermill.
One further grinder-mixer design in this area discharges the settled out particulate matter from the separator back into the infeed hopper of the hammermill. This type of a system tends to promote plugging in the separator outlet since the material being fed into the hammermill for grinding prevents the particulate matter from easily discharging from the separator outlet.
Additionally, the grinding of crop materials in a hammermill naturally generates some heat as the kinetic energy used to drive the hammermill is converted partially into thermal energy. This heat is generally retained in the ground crop material particles and transferred with them into the mixing tank. Traditional grinder-mixers employ grinding and dust collection systems that generally tend to promote the buildup of this heat in the crop material, especially when plugging occurs. When the grinder-mixer is left outside overnight, the heat that is retained within the mixing tank produces condensation on the inside of the tank when the outside air temperature naturally drops. This condensation will cause any crop material in the tank to sour, especially in the case of crops such as barley and oats. This causes the feed mixture to be less palatable and it usually is shunned by the livestock for whom it is intended. This can result in considerable quantities of feed mixture being wasted.
The foregoing problems are solved in the design of the apparatus comprising the present invention by providing for an improved dust collection system having a fan that is mounted on the front side of the grinding means and returns the settled out crop material from the cyclone separator to the top of the hammermill housing where it is distributed equally across the entire length of the hammermill.